Light micrograph of resin beads used in High Pressure Liquid Chromatography (HPLC), a technique for separating closely-related components from a sample solution. In this case the beads are coated with a hydophobic, waxy substance which has a long molecular backbone of 18 carbon atoms. The beads are packed into a column, usually a steel tube, through which the sample is pumped under pressure. Each component experiences an attraction to the beads which depends on its hydrophobic/hydrophilic properties, hence they emerge from the bottom of the column at different rates. Magnification: x400 at 35mm size.